This invention relates to a torque limiting clutch comprising a driving part and a driven part disengageably inter-connected in torque transmitting relationship by a torque transmitting element guided by a cage, a spacer movable by the cage into spacing relationship with said parts, on disengagement of the clutch by relative rotation between said parts in either direction, to maintain the torque transmitting element out of torque transmitting relationship with said parts and the clutch being re-engageable by relative rotation between said parts in the opposite direction, the clutch including inter-engageable abutments, on the cage and on one of said parts to inter-engage to cause said cage and one of said parts to rotate together during re-engagement on relative rotation between said parts in the reverse direction to the direction of disengagement.
Such a clutch will be referred to hereinafter as "of the kind specified", and an example is shown in GB-B-2080449 where these are two pairs of said inter-engageable abutments.
A problem has been encountered with such a clutch of the kind specified where the clutch is incorporated in a drive which has low inertia. In these circumstances when an operator reverses the drive to re-engage the clutch the speed of rotation of the part of the clutch connected to the motor is accelerated to such a speed that the abutments do not have sufficient time to re-engage. When the operator notices this lack of drive he switches off the motor and as the speed falls the abutments have sufficient time to start to move into interengagement but because this occurs as the speed is falling several attempts to engage sufficiently to lock in position may occur. The first few attempts will result in wear of the abutments which will eventually prevent re-engagement completely.
An object of the invention is to over come this problem.
The clutches described in the above referred to specification have the torque transmitting elements maintained in their receiving means by virtue of providing a taper to the bore in the cage in which they are received and biasing the cage by spring means towards the clutch part having the receiving means.
It has been found, however, that the use of springs to bias the cage plate in this way is not effective in all situations particularly where the receiving means comprise recesses separate to the torque transmitting recesses and of greater diameter and depth than the torque transmitting recesses.
Accordingly a further object of the invention is to over come this problem.